Diffuse large B-cell lymphoma (DLBCL) is the most frequent non-Hodgkin's lymphoma (NHL), accounting for 30 to 40% of diagnoses1. Its prognosis has significantly improved over the last decade, predominantly because of the addition of the Rituximab antibody to chemotherapy regimens2. Unfortunately, approximately one third of subjects do not respond to therapies or rapidly relapse, and a majority of them rapidly succumb from the disease3. These differences in clinical evolutions can, at least in part, be explained by the heterogeneity of this tumor, which regroups two major subtypes with different outcomes4. The first, termed germinal center B cell-like (GCB), develops from germinal center B-cells. It is the most curable, with a 5 years overall survival rate of nearly 75%. The second, termed activated B-Cell like (ABC), develops from late GC-B cells or plasmablasts. It is more aggressive and can only be cured in approximately 30% of subjects5.
If this GCB/ABC cell of origin (COO) classification has been described more than 10 years ago, it still has little influence on clinical practices. However, recent advances suggest that these tumors could soon benefit from targeted therapies. Signaling through the B-cell receptor (BCR) has for example been shown to be essential for ABC DLBCL cells survival, and specific inhibitors directed against major component of the NFkappaB pathway should rapidly become available in the clinics (ref Roschewski et al, Nature review 2014). Similarly, GCB DLBCLs could soon benefit from inhibitors of the BCL2 or BCL6 oncoproteins, and from therapies targeting their recurrent epigenetic abnormalities. Unfortunately, these lymphomas are morphologically undistinguishable in routine diagnosis, which is a major problem for the development of these therapies. Furthermore, array-based gene expression profiling, which is considered as the “gold standard” to discriminate these tumors, remains poorly transposable to routine diagnosis, and the surrogate immunohistochemical (IHC) algorithms which have been proposed are often considered poorly reliable (ref Ludenburg consortium De Jong J C O 2007 and Salles Blood 2011).